Chapter 16 – Schizophrenia and the Affective Disorders

Chapter 16

Schizophrenia and the Affective Disorders

Schizophrenia A serious mental disorder characterized by disordered

thoughts, delusions, hallucinations, and often bizarre behaviors

Afflicts ~1% of population Probably the most misused psychological term – literally

means “split mind”, so often confused with multiple personality disorder

Positive symptoms – symptoms evident by their presence Thought disorders – disorganized, irrational thinking (most

important symptom) Delusions – a belief that is clearly in contradiction to reality

Persecution – false beliefs that others are plotting against oneself Grandeur – false beliefs in one’s own power Control – belief that one is being controlled by others

Hallucinations – perception of a nonexistent object or event

Schizophrenia Negative symptoms – characterized by the absence of

behaviors that are normally present Flattened emotional response Poverty of speech Lack of initiative and persistence Inability to experience pleasure Social withdrawal

Heritability Both adoption and twin studies indicate that schizophrenia is a

heritable trait If there is a “schizophrenia gene”, then it must be triggered by

some type of env’tal event Study shows that higher paternal age is positively correlated

with diagnosis of schizophrenia

Pharmacology of Schizophrenia Dopamine hypothesis – suggest that schizophrenia is

caused by overactivity of DA synapses, probably those in the mesolimbic pathway

Effects of DA agonists and antagonist A drug used to prevent surgical shock, chlorpromazine, was

dramatically effective in reducing symptoms of schizophrenia Since this discovery, many other drugs have been developed

that relieve the positive symptoms of schizophrenia; All of these drugs block DA receptors

DA agonists act to produce positive symptoms of schizophrenia (e.g amphetamine, cocaine and L-DOPA)

The mesolimbic pathway is most likely involved in schizophrenia; could be caused by reinforcing effects of this pathway for any of the behaviors found with positive symptoms

Pharmacology of Schizophrenia Effects of DA agonists and antagonist

Schizophrenics often report feelings of elation and euphoria at the beginning of a schizophrenic episode, suggesting that this is caused by hyperactivity of DA neurons involved in reinforcement

Paranoid delusions may be caused by increased activity of the DA input to the amygdala

Amygdala is involved with conditioned emotional responses for aversive events

DA transmission abnormalities DA neurons may release more DA

Amphetamine administration caused the release of more DA in the striatum of schizophrenic patients; patients with greater amounts of DA showed greater increases in positive symptoms

There may be moderate increases in the numbers of D2 receptors, but it is unlikely that that is the cause of the disorder

Clozapine – an atypical antipsychotic drug; blocks D4 receptors in the nucleus accumbens

Pharmacology of Schizophrenia Long-term drug treatment

The symptoms of up to 1/3 of all schizophrenic patients are not substantially reduced by antipsychotic drugs

Many drugs produce serious side effects Until recently, all drugs caused at least some symptoms

resembling those of Parkinson’s disease: slow movement, lack of facial expression, general weakness

Tardive dyskinesia – a movement disorder that can occur after prolonged treatment with antipsychotic medication, characterized by involuntary movements of the face and neck

Caused by overstimulation of DA receptors Why would antagonists cause overstimulation of DA receptors?

Supersensitivity – the increased sensitivity of NT receptors; caused by damage to the afferent axons or long-term blockage of NT release

However, new drugs have been developed that do not produce these long-term side effects – atypical antipsychotic drugs (Clozapine)

Schizophrenia as a neurological disorder Whereas the positive symptoms are unique to

schizophrenia, the negative symptoms are similar to those produced by brain damage caused by several different means

Brain abnormalities in schizophrenia Patients with schizophrenia exhibit neurological symptoms

that suggest brain damage (e.g. poor control of eye movements, unusual facial expressions)

This suggests that schizophrenia may be associated with brain damage of some kind

MRI and CT studies have found loss of brain tissue in patients with schizophrenia

Relative size of lateral ventricles was more than twice the size of control subjects

Schizophrenia as a neurological disorder Possible causes of brain abnormalities

Why do less than ½ the children of schizophrenic patients become schizophrenic?

Perhaps what is inherited is a susceptibility to environmental factors that may lead to some type of brain damage

Development of disorder is most likely caused by interaction b/t genes and environment

However, people can develop schizophrenia without and family history

Epidemiology – study of distribution and causes of diseases in populations; try to correlate disease frequencies with factors that are present in the env’t

People born during late winter and early spring are more likely to develop schizophrenia – seasonality effect

Possibly caused by higher likelihood of mother contracting viral illness

Also more likely to occur in cities rather than countryside

Schizophrenia as a neurological disorder Possible causes of brain abnormalities

People born far from the equator are more likely to develop schizophrenia – latitude effect

Decreased winter temp may magnify seasonality effects Famine (especially thiamine deficiency) during pregnancy may

cause schizophrenia in offspring Underweight women are more likely to give birth to babies

who later develop schizophrenia; low birth-weight babies have higher incidence of schizophrenia

Vitamin D deficiency Rh incompatibility

Red blood cells of Rh-positive person contain Rh factor If fetus is Rh incompatible with mother, then increased likelihood of

schizophrenia in offspring

Schizophrenia as a neurological disorder Evidence for abnormal brain development

Prenatal brain development of children who become schizophrenic is not normal

Reports of both behavioral and anatomical abnormalities Children who later became schizophrenic displayed more negative

affect in their facial expressions and were more likely to show abnormal movements

Some monozygotic twins are discordant (i.e. one develops it, the other does not) for schizophrenia: difference in brain structure (one has larger ventricles, degeneration in specific regions of cerebral cortex)

Monochorionic (share one placenta) vs. dichorionic (separate placentas) in monozygotic twins: concordance rate for schizophrenia was lower in dichorionic vs. monochorionic

Schizophrenia not caused by degeneration, but by a rapid loss of brain volume during young adulthood

Does not involve death of neurons, but a loss of neuropil,the network of dendrites and axons in the brain

Schizophrenia as a neurological disorder Positive and negative symptoms: Prefrontal cortex

Is there a relationship b/t the 2 categories of symptoms? Negative symptoms caused by hypofrontality (decreased

activity of the frontal lobes), primarily in the dorsolateral prefrontal cortex

May be caused by decrease in release of DA in prefrontal cortex, mediated mostly by D1 receptors

Chronic abuse of PCP (indirect glutamate antagonist) causes a decrease of metabolic activity in frontal lobes

Chronic PCP treatment reduces DA activity in the prefrontal cortex, which in turn produces hypofrontality that appears to be responsible for the negative symptoms of schizophrenia

Prefrontal hypoactivity (neg. symptoms) causes mesolimbic DA hyperactivity (pos. symptoms)

Clozapine causes an increase in DA release in prefrontal cortex, and decrease of DA release in nucleus accumbens

Major Affective Disorders Affect – refers to feelings or emotions Major affective disorders – a serious mood disorder;

includes unipolar and bipolar disorder Bipolar disorder – characterized by cyclical periods of mania

(extreme elation) and depression (extreme despair); episodes of mania generally shorter than episodes of depression

Unipolar depression – consists of unremitting depression or periods of depression that do not alternate with periods of mania

Depression causes very little energy, crying, inability to experience pleasure, disturbed sleep, depressed bodily functions

Mania involves sense of euphoria, nonstop speech and motor activity, easily angered, go without sleep

Major Affective Disorders Heritability

The tendency to develop a major affective disorder is heritable A single dominant gene is responsible for susceptibility to

developing bipolar disorder Physiological treatments

MAO inhibitors Drugs (e.g. Iproniazid) that inhibit the activity of MAO, the enzyme

that destroys excess monoamine transmitter substance within terminal buttons, increase the release of DA, NE and 5-HT

Have serious side effects, e.g. cheese effect with pressor amines Tricyclic antidepressants

Inhibit the reuptake of 5-HT and NE by terminal buttons This keeps the NT in contact with the postsynaptic receptor, thus

prolonging the postsynaptic potentials Specific serotonin reuptake inhibitors (SSRI)

Inhibit reuptake of 5-HT Widely prescribed for depression and for symptoms of OCD and

social phobia

Major Affective Disorders Physiological treatments

Electroconvulsive therapy (ECT) Electrodes placed on patients scalp deliver a jolt of electricity to

trigger a seizure Most effective with mania and depression Effects are rapid, as compared to drugs

Lithium Most effective in treating the manic phase of bipolar disorder Does not suppress normal feelings of emotion Does not impair intellectual processes Does have some side effects, including hand tremors, weight gain,

excessive urine production and thirst Some patients with bipolar disorder have trouble continuing with

medication Those who cannot tolerate side effects can take carbamazepine, an

anti-seizure medication

Major Affective Disorders Role of monoamines

Monoamine hypothesis: hypothesis that states that depression is caused by a low level of activity of one or more monoaminergic synapses

Since the symptoms of depression do not respond to potent DA agonists (e.g. amphetamine or cocaine), researchers have focused on NE and 5-HT

Depression can be caused by monoamine antagonists e.g. reserpine

Suicidal depression is related to decreased CSF levels of 5-HIAA, a metabolite of 5-HT that is produced when MAO breaks it down

Families of subjects with low levels of 5-HIAA were more likely to include people with depression

Suggests that 5-HT metabolism or release is genetically controlled and is linked to depression

Major Affective Disorders Role of monoamines

Tryptophan depletion procedure Depressed patients currently taking medication Gave low-tryptophan diet, follwed by an amino acid “cocktail”,

which would inhibit what little tryptophan was left from entering the brain

Tryptophan depletion caused most of the patients to relapse back into depression

However, recovered after resuming normal diet This has no effect on healthy, non-depressed subjects, but does

lower the mood of people with a family history of affective disorders

Major Affective Disorders A role for Substance P?

A peptide secreted as a NT and neuromodulator in several regions of the brain

May be involved in emotional behavior, the response to stress, and the symptoms of depression

Long-term admin of antidepressants cause a reduction of substance P levels in several regions of the brain

MK-869, a drug that blocks the receptor for substance P (NK1) shows a reduction in depressive symptoms

Substance P antagonists appear to act independently of drugs that reduce depression by blocking the reuptake of 5-HT and NE

Major Affective Disorders Evidence for brain abnormalities

Studies have found abnormalities in the prefrontal cortex, basal ganglia, and cerebellum of patients with unipolar depression, and abnormalities of the cerebellum in those with bipolar disorder

Found in young patients, which suggests the presence of a developmental abnormality or a degenerative process that occurs early in life

Repeated episodes of depression and mania caused an increase in the size of the lateral ventricles

The amygdala and several regions of the prefrontal cortex play a role in the development of depression

Activity of amygdala of depressed patients was correlated with the severity of their depression

Orbitofrontal cortex generally more active in depressed patients Subgenual prefrontal cortex shows a lower level of activation in

depressed patients; activity in this region is increased during manic episodes

Major Affective Disorders Evidence for brain abnormalities

Silent cerebral infarctions A small cerebrovascular accident (stroke) that causes minor brain

damage without producing obvious neurological symptoms Appears to be a major cause of late-onset depression (first occurs

later in life) Risk factors are similar for stroke (e.g. smoking, hypertension)

Major Affective Disorders Role of circadian rhythms

One of the most prominent symptoms of depression is disordered sleep

Sleep of depressed individuals is shallow, Stages 3 & 4 are reduced, Stage 1 is increased

REM sleep occurs earlier Selective deprivation of REM sleep alleviates depression

The effect occurs slowly like that of drugs Other treatments for depression suppress REM sleep, suggesting

that REM sleep and mood may be correlated Successful ECT treatments suppress REM sleep in depressed

patients Total sleep deprivation produces immediate effects

Perhaps, during sleep a substance is produced that has a depressogenic effect

Depressed patients whose moods fluctuate more often will benefit from sleep deprivation more

Major Affective Disorders Role of Zeitgebers

Seasonal affective disorder – a mood disorder characterized by depression, lethargy, sleep disturbances, and craving for carbohydrates during the winter season when days are short

Summer depression – a mood disorder characterized by depression, sleep disturbances, and loss of appetite

Seasonal affective disorder appears to have a genetic basis Molecular genetic studies suggest that seasonal affective disorder

may be linked to genes involved in production of the 5-HT transporter and the 5-HT2A receptor

SAD can be treated with phototherapy, treatment of exposing people to bright light for several hours a day